He said he was particularly concerned about children consuming pot that has been baked into food products.

"I want to make sure children don't get access to marijuana in that way or other ways," Brown said.

A group called ResponsibleOhio, made up of wealthy investors, is spearheading the pot legalization campaign in Ohio. The group is seeking voter approval for a state constitutional amendment that would legalize the drug.

If approved, the measure would allow 10 farms around the state to grow marijuana for sale in medical dispensaries and retail stores. Home growers would be able to get a $50 license to raise four plants at a time only for personal use.

Brown did not say he would vote against the measure if it makes it onto the November ballot. He said he wanted to study how marijuana legalization has worked in Colorado and find out more about how the Ohio proposal would work.

"I have significant concerns about it," Brown said. "It's a step that we should take with great caution."

Brown said he does support legalizing marijuana for medical purposes.

"The evidence is in that it works for a number of patients" to help manage their illnesses, the Ohio Democrat said.

Sen. Rob Portman, R-Ohio, strongly opposes legalizing marijuana for recreational purposes. He has said he supports spending less money on "prosecution and incarceration" of drug use and "more on prevention and treatment."

But legalizing marijuana is "the wrong message to send," Portman told reporters in May. "Instead we should be saying to young people, 'There is a better way for you to have a healthy and productive life and that's not to get into drug use.' "

Portman said he was also skeptical of efforts to legalize marijuana for medical purposes. He said many states have passed medical marijuana measures that are overly broad and open to abuse.